Therapy for the treatment of a heart failure is designed to resynchronize contractions of heart chambers (atrium and ventricle, and both ventricles) in order to improve the patient's well being by optimizing different phases of a hemodynamic cycle. A hemodynamic cycle includes: pre-ejection, isovolumetric contraction, systolic ejection, isovolumetric relaxation, and finally filling of a cavity.
To optimize cardiac hemodynamics, one should:                ensure a maximum filling time between the moment the aortic valve closes and the moment the mitral valve closes, and        allow a systolic time that ensures a maximum ejection time as compared to the pre-ejection time, a condition of effectiveness of a systolic phase.        
The optimization can be achieved by adjusting the atrioventricular delay and/or the interventricular delay. The atrioventricular delay, hereinafter referred to as “AV delay” (AVD), is the delay separating, during one cardiac cycle, an atrial event (e.g., an atrial contraction, either spontaneous or stimulated by the device) and the consecutive ventricular stimulation. The interventricular delay, hereinafter referred to as “VV delay” (VVD), is the delay separating, during one cardiac cycle, two ventricular stimulations respectively applied to the right and the left ventricles, said VV delay being adjusted so as to resynchronize the ventricular contractions—a technique known as CRT (Cardiac Resynchronization Therapy) or BVP (Bi-Ventricular Pacing).
EP 0 862 927 A1 and its US counterpart U.S. Pat. No. 5,995,870 (assigned to ELA Medical, now known as Sorin CRM) describes a method to adjust AVD and VVD parameters according to a ventricular contraction, detected by a sensor measuring representative variations of either the volume or either of the movement of the ventricular muscle fibers at the beginning of a systole and/or at the opening of one or both of the semilunar valves, in order to determine the moment of the opening. This detection may be operated by various types of sensors such as sensors for measuring an electrical impedance of the myocardium, contractility, and ventricular volume by magnetometry, and sensors for detecting the opening of a valve by ultrasonic transduction. These sensors may be mounted on an endocardial stimulation lead.
However, clinical experience shows that optimization of hemodynamic parameters, such as the filling time or the time of left pre-ejection are not always sufficient to achieve desired results. There is a close interrelationship between different phases of a cardiac cycle, however, the existing methods do not allow a correlation of the evolution of all cardiac phases to find optimal AVD and/or VVD parameter settings for a sufficient CRT.
The starting point of the present invention is the discovery by the inventor(s) that, for improving the hemodynamic status of a patient, optimization of hemodynamic parameters based on one of the cardiac phases is not sufficient, and a whole cardiac cycle is compromised instead of optimizing only a particular part of a cardiac cycle to the detriment of other parts of the cardiac cycle. Thus:                the optimization of the systole shall not reduce the filling time, and        the optimization of the filling time shall not reduce the effectiveness of the systole.        